A technology disclosed herein relates to a management method for a storage subsystem, more particularly, to a failover management method in a so-called NAS system.
There is conventionally known network attached storage (NAS) in which a storage system connected to a network is used by a plurality of client computers connected to the network as a shared disk. The NAS is composed of servers including a network interface and a disk device for storing data. Each of the servers constituting the NAS is also called NAS server or NAS node (in the description hereinbelow, will simply be referred to as node).
In order that services may continuously be provided even when a failure occurs in hardware or software constituting the NAS, two nodes generally constitute a cluster. When a failure occurs in one of the nodes constituting the cluster, the other one of the nodes takes over the service provision of the node in which the failure has occurred. As a result, provision of the service can be continued and an effect of the failure in the node to clients can be suppressed to a minimum level. The technique as described above is called failover.
In addition, there is also known a technique in which three or more nodes constitute a cluster. In this case, a single management server collectively manages the nodes in the cluster. Thus, when a failure occurs in the management server, there is a problem that the cluster stops functioning. This problem is called single point failure. For avoiding the single point failure, JP 2006-323526 A discloses a technique of monitoring the management server by nodes other than the management server in the cluster, and causing another node to operate as the management server when a failure occurs in the management server.